It is generally known that consumers' demand (and value) for a particular gemstone is affected by the characteristics of that gemstone, such as, carat weight, clarity, cut and color. Clarity relates to the number, location and severity of inclusions in the gemstone. Color, in the case of diamonds, for example, refers to the whiteness or fancy color of the diamond, such as blue or pink. Large gemstones without inclusions are more rare and, thus more valuable. Often, carat weight is the most important characteristic of the gemstone to consumers, as carat weight relates to the size of the gemstone. As a result, diamond cutters, for example, have long focused on carat weight when cutting diamonds from a rough diamond. Frequently, diamond cutters may cut a larger diamond, for example, a 1.0 carat diamond that is less brilliant and is far from the ideal proportions rather than cutting a more brilliant, better proportioned smaller diamond, such as a 0.95 carat diamond. The primary reason is the difference in price between a diamond slightly under one carat and an one carat diamond is significant to the diamond cutter.
The cut of the gemstone effects the brilliance of the gemstone. Consumers generally dislike non-brilliant gemstones. Accordingly, more brilliant gemstones are desirable and valuable. Brilliance is defined by external brilliance as well as internal brilliance. External brilliance generally refers to the amount of light reflected from the table or outer surface of the diamond. On the other hand, internal brilliance refers to light entering the crown or table of the gemstone and reflecting back out through the top or crown of the gemstone as dispersed light.
In response to consumer demand, diamond cutting prior to the twentieth century was primarily concerned with maximizing carat weight. In 1919, however, Marcel Tolkowsky publicized his theoretical analysis for the most attractive cut for round brilliant diamonds. Today's “ideal cut” diamonds correspond to Mr. Tolkowsky's proportions for a round brilliant diamond, which are acclaimed to produce the ideal brilliant diamond. Specifically, Mr. Tolkowsky determined that the ideal proportions for a round brilliant diamond are: a 34.5° crown angle, a 40.75° pavilion angle, a depth of 59.3% (16.2% of the depth comprised of the crown and 43.1% of the depth comprised of the pavilion), and a 53% table based on the diamonds overall diameter. These proportions are now regarded as the most brilliant and beautiful diamond dimensions.
FIG. 1 generally depicts an “ideal cut” round brilliant diamond 10. Typically, the diamond 10 has 58 facets, including a culet 7. The diamond 10 has a length (or diameter) L as shown in FIG. 1. A table 5 is located at one end of the diamond 10 and has a length LI, which is typically measured by the percentage of the total length L of the diamond 10. As set forth by Mr. Tolkowsky, the “ideal cut” diamond 10 has a table of 53%. The diamond 10 has a crown 3 extending from the table 5 to a girdle 2. The girdle 2 is located at the intersection of a pavilion 4 and the crown 3. The crown 3 intersects the girdle 2 at an angle of 34.5°.
Today, the evaluation of the cut of the diamond is determined by reviewing the total proportion, symmetry and polish of the diamond. Table 1 illustrates how diamond cuts are evaluated and classified by proportions of the diamond. Class 1 diamonds are regarded as having a nearly ideal cut, while Class 4 diamonds are regarded as having a poor cut. As shown by Table 1, diamonds corresponding to Tokowsky's proportions are regarded as Class 1 diamonds.
TABLE 1Class 1 Through Class 4 Diamond ComparisonsClass1234Table53%-60%61%-64%51%-52%- 51%(stones under65%-70%70% +0.50 ct.may go to 62%)Crown34  -35−32−-34−30−-32−- 30−36−-37−37− +Girdlemedium-thin-thickv. thin-ext. thin-sl. thickv. thickext. thickPavillion43%42%-44%41%- 41% or45%-46%46%+Culetnone-mediumsl. largelargevery largeFinishvery good-goodfairpoorexcellent
As illustrated in Table 1, it has been the view of diamond professionals that crown angles below 30 degrees are not desirable, and as such those diamonds are identified as Class 4 diamonds. Other characteristics negatively effecting the diamond, include changing the proportions of the pavilion and the table.
It has long been the belief of diamond professionals that an ideal cut diamond is the most brilliant diamond. Generally, light directed into an ideal cut gemstone is reflected by the pavilion. The light or at least a portion of the light returns to the table and crown and radiates out of the gemstone. Light entering the top table of the gemstone travels in a u-shape within the gemstone and exits the top of the gemstone, but light entering the crown (“C light”) travels to the immediate pavilion, is then reflected to the opposite pavilion, and leaks therefrom (“Co light”). However, a small portion of C light will be reflected by the opposite pavilion and radiate from the top of the gemstone (“Ct light”). A deep cut gemstone causes light entering from the top to travel in an L-shape within the gemstone and to exit the side of the gemstone. A shallow cut gemstone causes light entering from the top to curve slightly back out the bottom of the gemstone. If light leaks or otherwise exits the sides or bottom of the gemstone, the gemstone has less brilliance.
FIGS. 2A-2C illustrate how light is reflected and refracted into, through and ultimately out of a round diamond. FIG. 2A illustrates light entering a diamond that is cut too deep, for example, deeper than the ideal diamond 10. As a result, light is lost through the pavilion 4. If the diamond is cut shallower than the ideal cut diamond 10, light does not reflect within the diamond as shown in FIG. 2B. The ideal cut diamond 10, as illustrated for example in FIG. 2C, reflects three types of light: (1) light from the table 5 to the table 5 (“T-T light”), (2) light from the crown 3 which leaks from the opposite pavilion (“C-Co light”), as well as (3) a portion of the light from the crown 3 which is reflected from the opposite pavilion to the table 5 (“C-Ct light”). The traditional ideal cut diamond 10, thus, is not fully capable of reflecting light from the crown 3 to the crown 3 (“C-C light”)
Although Tolkowsky's theory has been claimed to produce the most beautiful round cut diamond 10, such diamonds tend to have a bright table 5, but a less bright crown 3, especially toward the girdle 2. As illustrated in FIGS. 3A and 3B, the ideal cut diamond 10 is bright on the table 5, but less bright on the crown 3. One of the primary reasons is that the ideal cut diamond 10 is incapable of reflecting C-C light.
Accordingly, the present invention departs from conventional diamond proportions to improve the brightness of the crown. For example, the present invention departs from the crown angles of the conventional ideal cuts in order to guide reflected light to the crown. In addition, in at least one embodiment, the present invention improves the brightness of gemstones by causing light to enter the gemstone with oblique angles as well as loosely focusing the returning light to the observer's eyes by expanding the crown angles to obtain a parabolic focal effect.
The present invention also departs from the conventional focus of the carat weight of the gemstone. By departing from the conventional diamond proportions, the present invention allows the cutting of smaller mass gemstones that have diameter sizes that typically correspond to larger mass gemstones. To this end, the present invention may also allow more well proportioned gemstones to be produced from a rough gemstone.